Various types of electrochemical cells using metal as the fuel are known such as metal-air, Pb-acid, and Ni—Zn batteries. For example, a metal-air cell typically comprises a fuel electrode at which metal fuel is oxidized and an air breathing cathode at which oxygen from ambient air is reduced during a discharge mode. During a charge mode, the metal fuel is reduced and electrodeposited at the fuel electrode, thereby storing the metal fuel for a future discharge process. The electrochemical cell comprises an electrolyte for supporting reactions of the oxidized/reduced ions. During discharge, the concentration of the reducible metal species in the electrolyte increases towards a saturation point. A significant challenge with these types of cells is non-uniformity of charge/discharge and electrode passivation due to high concentrations of metal fuel ions in the electrolyte, resulting in poor cycling behavior. On cycling, build-up of metal fuel (e.g. formation of dendrites) causes problems including premature formation of electrical connections between electrodes, reduced charge capacity and lower overall cell efficiency in the battery.
Among other things, the present application endeavors to provide an effective and improved way of operating electrochemical cells comprising electrodeposited metal fuel, minimizing passivation of the metal fuel on cycling, eliminating the areas of metal fuel buildup at the fuel electrode, and effectively conditioning the fuel electrode to a fresh chargeable condition.